<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <script src="../js/react.development.js"></script>
    <script src="../js/react-dom.development.js"></script>
    <script src="../js/babel.min.js"></script>
  </head>
  <body>
    <div id="test"></div>

    <script type="text/babel">
      /* 
      1. 字符串
      2. 回调函数
      3. 调用React.createRef方法创建构造器
     */
      class UserInfo extends React.Component {
        inpEl = React.createRef();

        showInfo = () => {
          let { current: input } = this.inpEl;
          console.log(input.value);
        };
        render() {
          return (
            <div>
              <input type="text" ref={this.inpEl} />
              <br />
              <button onClick={this.showInfo}>增加</button>
            </div>
          );
        }
      }

      ReactDOM.render(<UserInfo />, document.getElementById("test"));
    </script>
  </body>
</html>
